Detection of immunoglobulin E in feces by immunoprecipitation, and characterization of associated non-immunoglobulin precipitins.

All concentrated human fecal extracts tested formed precipitates in double immunodiffusion with goat antiserum to IgE, as well as with normal goat sera. However, no such precipitates were formed by fecal extracts and rabbit sera. IgE precipitates obtained with both goat and rabbit antisera to IgE showed reactions of non-identity with the former precipitates which seemed to represent complexes of trypsin or chymotrypsin in feces and an alpha-protein in goat sera. This alpha-protein, which was responsible for the non-immunoglobulin precipitations, was different from human alpha 1-antitrypsin. The trypsin-like components in feces had low molecular weights, and might represent degradation products of trypsin or chymotrypsin. After using a second labelled antiserum, precipitates between rabbit antiserum to IgE and extracts of feces could be visualized by means of autoradiography. They were seen in fecal extracts in which IgE could also be determined by a double-antibody paper radioimmunoassay technique (paper radio immunosorbent test; PRIST). Since the concentrations measured by a radioactive single-radial immunodiffusion method correlated to some extent with the PRIST concentrations, the latter precipitates were likely to represent IgE in feces.